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In 1963, a 21-year-old physicist named Stephen Hawking
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was diagnosed with a rare neuromuscular disorder
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called amyotrophic lateral sclerosis, or ALS.
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Gradually, he lost the ability to walk,
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use his hands,
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move his face,
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and even swallow.
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But throughout it all, he retained his incredible intellect,
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and in the more than 50 years that followed,
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Hawking became one of history's most accomplished and famous physicists.
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However, his condition went uncured
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and he passed away in 2018 at the age of 76.
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Decades after his diagnosis,
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ALS still ranks as one of the most complex,
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mysterious,
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and devastating diseases to affect humankind.
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Also called motor neuron disease and Lou Gehrig's Disease,
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ALS affects about two out of every 100,000 people worldwide.
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When a person has ALS,
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their motor neurons,
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the cells responsible for all voluntary muscle control in the body,
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lose function and die.
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No one knows exactly why or how these cells die
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and that's part of what makes ALS so hard to treat.
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In about 90% of cases,
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the disease arises suddenly, with no apparent cause.
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The remaining 10% of cases are hereditary,
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where a mother or father with ALS passes on a mutated gene to their child.
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The symptoms typically first appear after age 40.
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But in some rare cases, like Hawking's, ALS starts earlier in life.
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Hawking's case was also a medical marvel because of how long he lived with ALS.
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After diagnosis, most people with the disease live between 2 to 5 years
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before ALS leads to respiratory problems that usually cause death.
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What wasn't unusual in Hawking's case was that his ability to learn,
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think,
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and perceive with his senses remained intact.
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Most people with ALS do not experience impaired cognition.
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With so much at stake for the 120,000 people
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who are diagnosed with ALS annually,
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curing the disease has become one of our most important scientific
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and medical challenges.
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Despite the many unknowns,
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we do have some insight into how ALS impacts the neuromuscular system.
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ALS affects two types of nerve cells called the upper and lower motor neurons.
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In a healthy body, the upper motor neurons,
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which sit in the brain's cortex,
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transmit messages from the brain to the lower motor neurons,
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situated in the spinal cord.
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Those neurons then transmit the message into muscle fibers,
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which contract or relax in response,
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resulting in motion.
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Every voluntary move we make occurs
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because of messages transmitted along this pathway.
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But when motor neurons degenerate in ALS,
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their ability to transfer messages is disrupted,
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and that vital signaling system is thrown into chaos.
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Without their regular cues, the muscles waste away.
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Precisely what makes the motor neurons degenerate
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is the prevailing mystery of ALS.
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In hereditary cases, parents pass genetic mutations on to their children.
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Even then, ALS involves multiple genes
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with multiple possible impacts on motor neurons,
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making the precise triggers hard to pinpoint.
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When ALS arises sporadically, the list of possible causes grows:
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toxins,
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viruses,
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lifestyle,
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or other environmental factors may all play roles.
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And because there are so many elements involved,
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there's currently no single test that can determine whether someone has ALS.
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Nevertheless, our hypotheses on the causes are developing.
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One prevailing idea is that certain proteins inside the motor neurons
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aren't folding correctly,
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and are instead forming clumps.
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The misfolded proteins and clumps may spread from cell to cell.
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This could be clogging up normal cellular processes,
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like energy and protein production, which keep cells alive.
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We've also learned that along with motor neurons and muscle fibers,
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ALS could involve other cell types.
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ALS patients typically have inflammation in their brains and spinal cords.
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Defective immune cells may also play a role in killing motor neurons.
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And ALS seems to change the behavior of specific cells
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that provide support for neurons.
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These factors highlight the disease's complexity,
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but they may also give us a fuller understanding of how it works,
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opening up new avenues for treatment.
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And while that may be gradual, we're making progress all the time.
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We're currently developing new drugs,
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new stem cell therapies to repair damaged cells,
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and new gene therapies to slow the advancement of the disease.
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With our growing arsenal of knowledge,
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we look forward to discoveries that can change the future
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for people living with ALS.